JP2006265051A - Optical device forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical device forming method by which a glass material is heated for a shorter time compared to the heating by the heat transfer from a usual forming mold and the heat radiation from the forming mold and a drum mold and exhibiting more controllability compared to the heat radiation of a halogen lamp or the like. <P>SOLUTION: In the optical device forming method carried out by press-forming a preform of the glass material before forming with a pair of the forming mold, the optical device is formed by being pressed after the preform is charged in a forming cavity and a member having a temperature equal to or above that of the preform in the charging is brought into contact with a surface of the preform where a non-optical functional surface is to be formed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a molding method of an optical element such as a camera / video lens, an optical scanning lens for an image forming apparatus, and a prism.

  The technology for manufacturing a lens by press molding of a glass material without the need for a polishing process eliminates the complicated process required in conventional manufacturing, and makes it possible to manufacture a lens easily and inexpensively.

  In such a pressing method, generally, an upper mold member and a lower mold member for molding are used, a glass material is inserted into the mold cavity, and the atmosphere is changed to a non-oxidizing atmosphere, for example, nitrogen to prevent oxidation of the mold member. The atmosphere is heated to a predetermined temperature suitable for molding, that is, until the molding material viscosity is log η = 8 to 12, press molding is performed at a predetermined pressure, and the shape of the molding surface of the molding die is changed to that of the molding glass material. Transfer to the surface. During this heating, the glass material is heated by heat conduction from the lower mold member and heat radiation from the upper mold member, the lower mold member, and the trunk mold. At this time, when the shape of the molding surface and the surface shape of the glass material are close, and the gap between the molding surface and the glass surface is small, the heat transfer is good, and the temperature of the molding surface of the glass material is the upper mold member, the lower mold member, The temperature is close to that of the body mold.

  Then, the mold and the molded glass optical element are cooled to a temperature sufficiently close to the transition temperature of the glass material, and then the pressing pressure is removed, the molding mold is opened, and the molded glass optical element is taken out.

  In particular, this press molding method has recently been adopted not only for optical elements such as aspherical lenses but also for non-axisymmetric lenses such as f-θ lenses and prisms.

  For example, in the molding apparatus described in Patent Literature 1 or Patent Literature 2, a molding die devised for accurately molding an optical element having an axially asymmetric surface having a toric surface, an anamorphic surface, or the like on both surfaces or one surface is presented. Yes.

  In Patent Document 3, an inlay structure is formed of a cylindrical shape of a square hole that is not divided and a rectangular upper and lower mold member that fits correspondingly, and a glass material is filled and pressed into the rectangular cavity. Thus, a required rectangular optical element is formed.

JP-A-6-256025 Japanese Patent Laid-Open No. 11-100220 JP-A-2-41790

  Thus, when glass is heated to form an optical element, the glass material is heated mainly by heat conduction from the lower mold member and heat radiation from the upper mold member, the lower mold member, and the trunk mold as described above. However, Patent Document 3 proposes a method for forming an optical element that can apply radiant heat to a glass material from the outside with a halogen lamp or the like to heat and soften the glass material to a desired temperature.

  However, in this method, the amount of the infrared rays transmitted through the halogen lamp through the glass material is lost, and the transmitted infrared rays heat the mold, thereby reducing the temperature controllability of the mold. was there.

  The present invention has been made in view of the above-mentioned problems, and the intended process is that the heating time is shorter than the heat transfer from the normal mold and the heating of the glass material by the heat radiation from the mold and the barrel mold. Another object of the present invention is to provide an optical element molding method that realizes heating of a glass material that has better controllability than thermal radiation of a halogen lamp or the like.

  In order to achieve the above object, an invention according to claim 1 is an optical element molding method in which a preform which is a glass material before molding is pressure-molded with a pair of molding dies, and the preform is placed in a molding cavity. After the charging, the optical element is formed by bringing a member having a temperature equal to or higher than the preform temperature at the time of charging into contact with a surface forming the non-optical functional surface of the preform and then pressing it.

  The invention according to claim 2 relates to the optical element molding method according to claim 1, wherein the surface forming the non-optical functional surface of the preform has a glass transition point temperature or higher, preferably a yield point temperature or higher. A member having a temperature equal to or lower than the softening point temperature is brought into contact and then pressed to mold the optical element.

  When the method of the present invention is used, the heating time is shorter compared to heating of the glass material by heat transfer from a normal mold and heat radiation from the mold and the barrel mold, and controllability compared to heat radiation of a halogen lamp or the like. Good glass material heating is realized.

  In particular, when a non-axisymmetric lens or the like such as an f-θ lens or a prism is press-molded, the surface that forms the non-optical functional surface of the preform that is a glass material is often a flat surface. This preform heating method is particularly effective.

  Next, an optical element molding method and molding apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows an embodiment of an optical element molding apparatus according to the present invention. Here, reference numeral 1 is an upper mold, 2 is a lower mold, and 3 is a barrel mold having a pair of upper and lower forming mold guide mechanisms and a heating mechanism. Reference numeral 4 denotes a preform made of a glass material, which has a shape that approximates the shape of the optical element after molding, and a surface 5 that forms a non-optical functional surface is an approximate plane. In the present embodiment, the preform is a phosphate glass, the transition point temperature is 380 ° C., the yield point temperature is 407 ° C., and the softening point is 440 ° C. Reference numeral 6 denotes an opening provided in a body mold for handling glass materials and fine scenery. The optical element that is press-molded by the molding apparatus is a rectangular lens.

  Reference numeral 7 denotes a heating device that heats the preform 4, and the preform 4 is brought into contact with the approximate plane portion 5 and heated by contact until just before the preform 4 is press-molded.

  Reference numeral 8 denotes a side window mold in which the surface 5 is formed by sliding after the preform has been heated by the preform heating apparatus.

  Next, an optical element molding method of the present invention to be performed using the optical element molding apparatus having the above structure will be described.

  First, the preform 4 having a shape similar to that of a molded product is adsorbed by a handling device (not shown), enters the cavity that is the inner space of the molding die through the opening 6 of the barrel die, Place on mold 2. At this time, the temperature of the preform 4 is 380 ° C. or less which is the glass transition temperature.

  Next, the preform heating device 7 is maintained at 420 ° C. ± 10 ° C., which is not less than the preform temperature at the time of charging, and in this embodiment is not less than the yield point of the preform 7 and not more than the softening point. The preform is brought into contact with the preform side surface 5 through the mold opening 6 and heated. At the same time, a heater (not shown) in the body mold 3 causes the upper mold 1 and the lower mold 2 to be optimally molded, for example, a temperature at which log η = 8 to 10 in terms of glass viscosity. Heat to 420 ° C.

  When the temperature of the preform 4 and the molding upper and lower molds 1 and 2 are suitable for molding, for example, the glass viscosity is log η = 8 to 12 at a temperature of 420 ° C. in this embodiment, the heating device 7 is connected to the barrel opening. 6, the side window mold 8 is slid to close the trunk mold opening, the lower mold 1 is lowered, and the preform is press-molded.

  In this way, after the preform is placed on the lower mold, the preform is heated with a heating device and then molded, so that the preform can be heated to the molding temperature in a short time as shown in FIG. It is possible to mold to the final molded product.

It is a structure front view of the shaping | molding die which shows embodiment of this invention. It is a structure side view of the shaping | molding die which shows embodiment of this invention. It is a structure perspective view of the shaping | molding die which shows embodiment of this invention. It is a temperature-time graph which shows the temperature rising process of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper mold | type 2 Lower mold | type 3 Cylinder mold 4 Preform which is glass material 5 Preform approximate plane which forms a non-optical functional surface after shaping | molding 6 Opening part provided in the trunk | drum 3 7 Heating apparatus which heats the preform 4 8 Side window type

Claims (2)

In an optical element molding method in which a preform which is a glass material before molding is pressure-molded with a pair of molding dies,
After the preform is put into the molding cavity, a member having a temperature higher than the preform temperature at the time of charging is brought into contact with the surface forming the non-optical functional surface of the preform, and then pressed to mold the optical element. An optical element molding method comprising:   A member that is not lower than the glass transition temperature of the preform, preferably higher than the yield point temperature and lower than the softening point temperature, is brought into contact with the surface that forms the non-optical functional surface of the reform, and then pressed to mold the optical element. The optical element molding method according to claim 1, wherein:

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